Hydraulic pump



June 7, 1949. P, HAAHR 2,472,529

HYDRAULIC PUMP Filed May 21, 1947 2 Sheets-Sheet 1 June 7, 1949. HAAHR 2,472,529

. HYDRAULIC PUMP Filed May 21, 1947 2 Sheets-Sheet 2 Patented June 7, 1949 [TED STATES PATENT OFFICE Application May 21, 1947,, Serial Nm 714%,434 In Denmark February 9, 1946 Section I, PublicLaw 690;- Rugust 8, 1946 Patent expires February 9 1 9756 (CL. 10.311)l 6. Claims. 1;

The: present, invention relates to; arrangements i-nlwdraulic. presses: oi the type having; a lowpressnree pumpand: a. high-pressure pump.

. My; invention. especially relates: to arrangements; of: the: kind inwhich are provided means for utilizing' the low-pressure pump as a. feeding pnrn-p tenths-high.- pressure pump.

' .Irc arrangements of the; kind. described above, a spring loaded valve is provided for discharging the excess fluid; from; the. low-pressure pump opemtmg, as feeding; pump: for the highpressure' pump.

It; is the main obiect of; my invention to pro"- vidaan improvement-,1 of the arrangement of the kind: referred to in which theweiliciency can be increased; compared with. the knownarrangements;

A. further objectv of my; invention is; to provide improvements in which an increased efiiciency can bo-obtained by, means of; a simple; and reliable construction.

The invention is.- illustrated in the drawing in which Fig. 1 is a schematical view of the pipe line connectionsin a press including a valve. device in accordance with this invention and I Fig, 2.is-; an enlargedsectionof thevalve device.

ltd-Fig.1, 4. denotes a low-pressure pump which may be. all gear and-l 51 is. a high-pressure pump. The drivingshaftsot these. pumps are mechanically coupledby means of. a. coupling 6 and are driveni'n any, convenient manner. These pumps serve. to. generate pressure fluid. for a... hydraulic press cylinder "the piston of which is. denoted by 3. Thepresscylihder: 2 is by means of pipe lines l2 and 1'3 connected with a reversing: valve I'l' through which pressure fluid can be supplied either to the upper side or' the lower side of' the press piston.3, as the casemay'be. The inlet. of the reversing valve H is by meanszof' the pipe line l4 connected: with a" valve device IS, the details of which will be-apparentirom Fig; 2'.

'The'pipe. line H" communicates inside the valve '(i'evl'ce l5with a space I'B communicating in its turnthrough anon-returnvalve 11' with another space; 18; The non-return valvel'l'is' normally held" in: its cl'osedpcsi'tion bymeans" of a spring P9 and its lift isllmitedby an abutment 20. The space l8 communicates" directly with the delivery side ofthe low pressure pump 4" and communicates further through a non-retum valvell with a return line 22tothe fluid reservoir (not shown) ofthepress. plant. The: non return" valve 21* is loaded Icya." relatively heavy spring"23* the ten-'- sion of whichcambeivariedl by a bushing 24 constituting abutment. for the spring. 23 being screwed toor fro in a. case 2& enclosing the non.- return: valve and its spring. Obviously the ten.- sion: on the spring 2a determines the pressure at the; delivery-sidaoi thelow-pressure pump, as. the non-return valve. wilL be lifted. soas to connect the delivery-side of. the low-pressure pumpwith the return. lines: 22' when; the said pressure will have: attained a. certain value.

As will 'beeapparenti from. Fig. I the: space l8 also comtmunicates:- through. a. pipe. line 26 with the inlet oi the highrpressure pump 5. The. delivery side of this. pump communicates. through a pipe line! 21: with thespacet6 in-the; valve device iii; The; non-return valve 2.! abuts as shown in Fig. 2 against one endof a. piston 28- which is slidably mounted; in alcyslinder 29- communicating througha pipalineriifliwith. the pipeline M. A pipe line- 3is communicating with. a low-pressure manometer (not shown) openscintov the space 18 in the-valve device. 15- and: apipe line 32- connects the: space- H5: at. the valve device with a highpressure.manometer (not shown).

it. control-valve, 33 isinserted: in; the pipe line is: and servesv to control: an: eiector. 9 for electing thework after. ithas been. actedon by the press.

The press; plant described. operates; as. follows. It is assumed that. the press. piston 3 is in its. uppermost position and the pumps 4 and. 5 are in operation.v Pressure fluid. will thenflow from the low-pressure, pump- 4: into: the. space H3 in the valve-device l5I and from: there pass; through the nonwretiirnzvalve H; to the said space I6; It will bearealized-thatthe high-pressulte;pump will thus eiiiect- .no:sulostairmail--work the pressure difierence betweenathepspaces t8 and. Iii-of the valve. device 15, being vergsmall; From the space iii of the valve device; Li: pressure fluid; will-flow through the-line Mote: thacontrol slide H: and: from the lattenthrongha. return lineflaback to the fluid reservoir-antheplant. Theapressure in the line I14; 'and' conseguentlpinethe space l6 will; thus be quite smaliand the: low-pressure pump 4-,. therefore, effects no substantial work, i. e. .boththe low-pressure pump 4 and the high-pressurapump Erwiliirila.

It now the: control slide: M is displaced; in such aimannerr as; tmprovidle connections. in the first: hand; hetweenfthe: Ma and the line ['2' and fiurthemnone betweem the: line.- 1134 and: the: return line--43 the pressure fluidf. supplied: through the line 'M wfll be fediito thesupper side of 'the press piston 3; 'the fluid below the: piston being at thfe same: time: allowed: to escape-through the: return 3 line 43. The piston 3 will therefore move downwards until it will meet resistance. Hereby the pressure in the pipe lines l2 and I4 is increased at the same time as the flow of fluid is substantially stopped. Hereby the non-return valve ll of the valve device I5 is closed and the fluid supplied from the low-pressure pump 4 now flows exclusively from the space l8 through the pipe line 26 to the high-pressure pump 5 which with an increased pressure feeds the fluid into the space it and from there into the pipe line [4. From here the pressure fluid will flow through the line 33 to the cylinder 29 whereby the piston 28 will be capable of lifting the valve 2| against the action of the spring 23 until the valve abuts against an adjustable abutment 4d. The space I8 of the valve device If: will thus communicate with the return line 22 whereby the pressure in the space i8 diminishes to the value determined by the lift of the valve 2|. The abutment M determining this lift is adjusted in advance in such a manner that the pressure in the space l8 will be sufficient to provide for the necessary feeding of the high-pressure pump '5. The low-pressure pump l will thus operate against a smaller counter-pressure while the high-pressure pump 5 takes over the essential part of the work. The pressure in the pipe line [4 and consequently in the press cylinder 2 is now increased in the course of a very short time, e. g. /2 second, to the maximum value determined by a safety valve (not shown) whereby the press acts upon the object placed therein. If now the control slide l I is displaced the pipe line I2 will be connected with an outlet 55, while the pipe line [4 will be connected with the pipe line l3. Hereby the pressure in the pipe line M will act upon the lower side of the piston 3 which will consequently be lifted without making any substantial resistance. The pressure in the pipe line H! will therefore decrease correspondingly which permits the spring 23 to close the valve 2| again. The pressure in the delivery pipe 2? of the high-pressure pump 5 decreasing at the same time to the same extent as the pressure in the pipe line Hi, the pressure in the space 18 will be greater than that in the space if i. e. the low-pressure pump 4 now takes the whole Work of lifting the piston 3. When the latter will be attained its uppermost position it will be stopped and the pressure will now increase in the pipe line 13 as well as in the pipe line H which would involve actuation of the high-pressure pump if no special measures were taken to prevent this. In the example shown these measures comprise the provision of a non-return valve ie in the piston 3 through which the space below the piston is allowed to communicate with the space above the piston in its turn communicating through the pipe line I2 with the outlet 45. Such safety valve may, however, also be arranged direct in the pipe lines It. In both cases the load on the valve should be such that the valve will open in response to a smaller pressure than that required for lifting the valve 2| of the valve device I5.

I claim:

1. An arrangement of the kind referred to comprising a low-pressure pump and a highpressure pump; means for feeding the highpressure pump from the low-pressure pump; an automatic spring-loaded valve for discharging the excess fluid from the low-pressure pump when operating as feeding pump for the highpressure pump; supplementary means for operating saidvalve under the influence of. the pressure at the delivery side of said high-pressure pump; and an abutment determining the maximum lift of said valve.

2. An arrangement of the kind referred to comprising a low-pressure pump and a high-pressure pump; means for feeding the high-pressure pump from the low-pressure pump; an automatic spring-loaded valve for discharging the excess fluid from the low-pressure pump when operating as feeding pump for the high-pressure pump; a piston for operating said valve under the influence of the pressure at the delivery side of said high-pressure pump; and an abutment determining the maximum lift of said valve.

3. An arrangement of the kind referred to comprising a low-pressure pump and a high-pressure pump; means for feeding the high-pressure pump from the low-pressure pump; an automatic spring-loaded valve for discharging the excess fluid from the low-pressure pump when operating as feeding pump for the high-pressure pump; a piston for operating said valve under the influence of the pressure at the delivery side of said high-pressure pump; an abutment determining the maximum lift of said valve; and means for subjecting said piston to the pressure in the feedingduct of the press when the low pressure pump operates as feeding pump for the high-pressure 4. An arrangement of the kind referred to comprising a low-pressure pump and a high-pressure pump; means for feeding the high-pressure pump from the low-pressure pump; an automatic spring loaded valve for discharging the excess fluid from the low-pressure pump when operating as feeding pump for the high-pressure pump; a piston for operating said valve under the influence of the pressure at the delivery side of said high-pressure pump; an abutment determining the maximum lift of said valve; and automatic means for subjecting said piston to the pressure in the feeding duct of the press when the lowpressure pump operates as feeding pump for the high-pressure pump.

5. An arrangement of the kind referred to comprising a low-pressure pump and a high-pressure pump; means for feeding the high-pressure pump from the low-pressure pump; an automatic spring loaded valve for discharging the excess fluid from the low-pressure pump when operating as feeding pump for the high-pressure pump; a piston for operating said valve under the influence of the pressure at the delivery side of said high-pressure pump; an adjustable abutment determining the maximum lift of said valve; and automatic means for subjecting said piston to the pressure in the feeding duct of the press when the low-pressure pump operates as feeding pump for the high-pressure pump.

6. In and for hydraulic presses, a low-pressure pump; a high-pressure pump; an automatic valve device comprising a spring loaded check valve for determinin the delivery pressure of said lowpressure pump; means responsive to pressure at the delivery side of said high-pressure pump to lift said check valve; means determining the lift of said check valve, said valve being movable independently of said lifting means under the action of pressure acting on it; means connecting the delivery side of said low-pressure pump with the inlet of said high-pressure pump; means connecting the delivery side of said low-pressure pump with the delivery side of said high-pressure pump; and means in said last named connection;

5 6 for closing the same at a certain pressure pre- UNITED STATES PATENTS 'vailing at the delivery side of the high-pressure Number Name Date Pump- 868,718 Smith Oct. 22, 1907 FOUL HAAHR- 5 1,049,894 Merrill Jan. 7, 1913 1,658,307 Small Feb. 7, 1928 REFERENCES CITED 1,814,857 Rosle July 14, 1931 The following references are of record in the 1,982,711 Vickers Dec. 4, 1934 file of this patent: 

